WO2015174921A1

WO2015174921A1 - Drive arrangement, system, and method for sludge removal

Info

Publication number: WO2015174921A1
Application number: PCT/SE2015/050551
Authority: WO
Inventors: Henrik WIKSTRÖM
Original assignee: Nordic Water Products Ab
Priority date: 2014-05-16
Filing date: 2015-05-18
Publication date: 2015-11-19

Abstract

A drive arrangement for an underwater traction assembly is provided. The drive arrangement comprises a drive wheel (242) and a drive unit (250) for driving the drive wheel (242). A housing (252) is provided above the drive unit (250). By designing the housing as an airtight diving bell, a simple yet reliable drive arrangement is achieved.A system for sludge removal in a circular settling tank is also provided.

Description

DRIVE ARRANGEMENT, SYSTEM, AND METHOD

FOR SLUDGE REMOVAL

Technical field

[0001 ] The present invention relates generally to a drive arrangement and a system for sludge removal. A method of operating a drive arrangement for an underwater traction assembly is also provided.

Background art

[0002] Settling tanks, such as circular settling tanks, are commonly used for treatment of water and wastewater. Water containing particles is introduced into the settling tank and the particles will settle to the bottom of the settling tank where they will form a sludge layer. The influent to the settling tank is divided into an overflow and an underflow. Settling tanks are expected to produce a reasonably clean overflow and a reasonably thick underflow. If the emphasis is on the clean overflow they are often named clarifiers and if the emphasis is on a thick underflow they are often named thickeners. The underflow normally leaves the settling tank through a central outlet in the bottom of the tank. The sludge that has collected on the tank bottom is transported to the underflow outlet by means of at least one sludge scraper. A sludge scraper normally consists of a scraper arm with one or more scraper blades attached. The scraper arm may be fixed to a central vertical shaft. The shaft is provided with a drive motor which rotates the shaft and scraper arm(s). Since the scraper blades are set at an angle relative to the scraper arm a transport of the sludge towards the center will result.

[0003] A prior art system for sludge removal is disclosed in the international patent publication No. WO2013/028123 A1 .

Summary of invention

[0004] An object of the present invention is to provide a drive arrangement and a system of the kind initially mentioned, wherein the mechanical drive arrangement is simplified. [0005] According to a first aspect of the invention there is provided a drive arrangement for an underwater traction assembly in a settling tank, the drive arrangement comprising: a drive wheel; a drive unit for driving the drive wheel; and a housing provided above the drive unit; the drive arrangement being

characterized in that the housing is airtight and designed as a diving bell.

[0006] In a preferred embodiment, the drive unit is a rotating hydraulic motor.

[0007] In a preferred embodiment, the drive unit is provided with a vertical shaft on which the drive wheel is attached.

[0008] In a preferred embodiment, the housing is provided with a closed top, preferably cylindrical.

[0009] In a preferred embodiment, the housing is provided with a circumferential flange at the lower edge thereof.

[0010] In a preferred embodiment, a base plate is provided, on with the housing is attached.

[001 1 ] In a preferred embodiment, the drive arrangement comprises any of the following: hydraulic supply means, supply means for compressed air and electrical cables.

[0012] In a preferred embodiment, the drive unit is mounted on an elevated platform.

[0013] According to a second aspect of the invention a system is provided for sludge removal in a circular settling tank having a side wall, the system

comprising: a rotatable drive ring adapted to be connected to a scraper arm provided with scraper blades, the drive ring having a plurality of engagement surfaces, a traction assembly comprising a drive wheel, wherein the drive wheel is provided with a plurality of engagement rolls adapted to engage the engagement surfaces of the drive ring during rotation of the drive wheel, which is characterized in that the traction assembly comprises a drive arrangement as described above. [0014] According to a third aspect of the invention a method is provided of operating a drive arrangement for an underwater traction assembly according to the invention, comprising the step of supplying air to the housing.

[0015] By use of the described drive arrangement, system and method, much simpler, more economical and more reliable sludge removal systems can be achieved.

Brief description of drawings

[0016] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

[0017] Figs. 1 and 2 show an overall view of a system according to the invention;

[0018] Fig. 3 is an enlarged view of a prior art drive arrangement comprised in the system of Figs. 1 and 2;

[0019] Fig. 4 is an enlarged view of a drive arrangement according to the invention comprised in the system of Figs. 1 and 2;

[0020] Fig. 5 is a sectional view of the drive arrangement shown in Fig. 4, and

[0021 ] Fig. 6 is a perspective view of the drive arrangement according to the invention without the housing mounted.

Description of embodiments

[0022] In the following, a detailed description of a system for sludge removal from circular tanks will be given.

[0023] Figs. 1 and 2 show an overall view of a system according to the invention, generally designated 100. The system, which is mounted in a circular settling tank 102 having a slanting or horizontal bottom 104 an essentially circular side wall 106, as is conventional. The system further comprises blades 1 10 attached to an arm 1 12 which in turn is attached to a vertical stub shaft 1 14. Optionally, skimmers (not shown) are also attached to the arm 1 12 or alternatively to the stub shaft 1 14.

[0024] Reference will now be made to Fig. 3, which is an enlarged view of a prior art drive arrangement 120 and which shows part of the circular wall 106 and the bottom 104.

[0025] Suspended to the side wall 106, there is provided a rotatable drive ring 130 which runs all around the side wall and which is part of a drive arrangement, generally designated 120. The drive ring 130 may be attached to the side wall by means of guides 132 or the like. The drive arrangement 120 also comprises a traction assembly 140 which is fixedly attached to the circular side wall 106 and which engages the drive ring 120 to, during operation, rotate the drive ring along the periphery of the circular settling tank 102. The drive ring and the traction assembly will be described in more detail below.

[0026] The drive ring 130 runs all along the circular wall 106 at the lower portion thereof, preferably about 0.5 - 1 .0 m from the bottom 104. The drive ring is provided with a plurality of engagement surfaces 134 with are spaced apart with predetermined distance, i.e., they are evenly distributed about the periphery of the settling tank 100. The engagement surfaces 134 may, as shown in Fig. 3, be an internal side wall of a respective aperture provided in the drive ring 130, although other configurations are possible as well. However, it is preferred that the engagement surfaces 134 are planar and extend radially from the centre of the drive ring 130 in order to eliminate or at least minimize radial forces on the drive ring 130, as will be explained below.

[0027] The traction assembly 140 comprises a drive wheel 142, which is mounted to a vertical drive wheel shaft 144. The drive wheel shaft is adapted to be rotated by a rotation arrangement, such as a motor/gear assembly. The drive wheel 142, which in the embodiment shown in the figures is star shaped, is provided with a plurality of engagement wheels or rolls 148. Adjacent engagement rolls 148 are provided on the drive wheel 142 at an equal mutual distance which is equal to the mutual distance between adjacent engagement surfaces of the drive ring 130. Thereby, these engagement rolls 148 are adapted to engage the engagement surfaces 134 of the drive ring 130.

[0028] Figs. 4 and 5 are a perspective and sectional view, respectively, of drive arrangement 220 according to the invention comprising a drive wheel 230 with its engagement rolls 248, interconnected by a plurality of bars 242. A drive unit 250 is provided inside a housing 252. The drive unit 250 is preferably a rotating hydraulic motor provided with a vertical shaft on which the drive ring 230 is attached. Thus, the drive arrangement shown in Figs. 4 and 5 operates in the same general way as the prior art arrangement shown in Fig. 3, but with a different drive unit.

[0029] The housing 252 is airtight and preferably cylindrical with a closed top in order to fit above the drive unit 250. Also, the housing is designed to withstand pressure from the liquid in which it is submerged. A preferred material for the housing is a corrosion resistant material, such as stainless steel. At the lower edge thereof, the housing is attached in a preferably airtight manner to a base plate at a split line 252a. To this end, in the preferred embodiment the housing 252 is provided with a circumferential flange 252b at the lower edge thereof. Thus, the housing 252 is airtight from the split line and up. The housing 252 is in the shown embodiment attached to the base plate by means of a screw joint, for example.

[0030] Hydraulic supply means, supply means for compressed air and/or electrical cables 250a enter the housing from below through an opening in the base plate.

[0031 ] Optionally, during operation, air, preferably compressed air, is supplied to the inside of the housing 252, which thereby functions as a diving-bell. This air may be supplied at a constant, slow rate or intermittently. By this, the interior of the housing is free or essentially free from water and moist, also in a submerged condition. However, in order to protect the drive unit 250 from any sludge or other particles that may enter through the split line between the housing 252 and the base plate 254, the drive unit 250 may be provided on an elevated platform 256, thereby creating a safety distance d between the drive unit 250 and the base plate [0032] In Fig. 6, the drive arrangement 220 is shown without the housing 250 mounted. The drive unit. In this figure, it is shown that the drive unit 250 is mounted on the elevated platform 256. Also shown is an optional tube or pipe 258 for filling the housing with pressurized air.

[0033] Preferred embodiments of a drive arrangement and a system for sludge removal have been described. It will be realized that these embodiments can be varied within the scope of the attached claims without departing from the inventive idea. Thus, it will be realized that although a rotating hydraulic motor has been shown and described, the drive unit may comprise alternative means, such as an electric motor, water hydraulics, a hydraulic piston etc. In the case of an oxygen consuming drive unit, oxygen must be supplied to the drive arrangement.

[0034] It has been described that air is supplied to create an overpressure in the housing. This air can be omitted without departing from the inventive idea, since the housing functions as a diving-bell also without additional supply of air, as long as the leakage is controlled.

[0035] It is preferred to have any supply means entering the drive arrangement from below, i.e., through the base plate. However, these supply means can also enter the drive arrangement through the housing as long as airtight entry points are ensured.

[0036] The drive arrangement has been described together with a system for sludge removal in a circular settling tank. It will be realized that this solution is also applicable to settling tanks having rectangular or square shape.

[0037] The housing has been shown with circular cross-section. It will be realized that it can has any cross-sectional shape, such as rectangular, as long as the drive unit is accommodated therein.

Claims

1 . A drive arrangement for an underwater traction assembly in a settling tank, the drive arrangement comprising:

- a drive wheel (230);

- a drive unit (250) for driving the drive wheel (242); and

- a housing (252) provided above the drive unit (250); c h a ra c t e r i z e d i n t h a t the housing is airtight and designed as a diving bell.

2. The drive arrangement according to claim 1 , wherein the drive unit (250) is a rotating hydraulic motor.

3. The drive arrangement according to claim 1 or 2, wherein the drive unit (250) is provided with a vertical shaft on which the drive wheel (230) is attached.

4. The drive arrangement according to any one of claims 1 -3, wherein the housing (252) is provided with a closed top, preferably cylindrical.

5. The drive arrangement according to any one of claims 1 -4, wherein the housing (252) is provided with a circumferential flange (252b) at the lower edge thereof.

6. The drive arrangement according to any one of claims 1 -5, comprising a base plate (254), on with the housing (252) is attached.

7. The drive arrangement according to any one of claims 1 -6, comprising any of the following: hydraulic supply means, supply means for compressed air and electrical cables.

8. The drive arrangement according to any one of claims 1 -7, comprising an elevated platform (256), on which the drive unit (250) is mounted on.

9. A system for sludge removal in a circular settling tank having a side wall (106), the system comprising:

- a rotatable drive ring (130) adapted to be connected to a scraper arm (1 12) provided with scraper blades, the drive ring having a plurality of engagement surfaces (134),

- a traction assembly (140) comprising a drive wheel (142), wherein the drive wheel (142) is provided with a plurality of engagement rolls (148) adapted to engage the engagement surfaces (134) of the drive ring during rotation of the drive wheel (142) c h a ra c t e r i z e d i n t h at the traction assembly comprises a drive arrangement according to any one of claims 1 -9.

10. A method of operating a drive arrangement for an underwater traction assembly according to claim 1 , comprising the step of supplying air to the housing.