WO1993025482A1

WO1993025482A1 - Liquid distribution mechanism

Info

Publication number: WO1993025482A1
Application number: PCT/GB1993/001254
Authority: WO
Inventors: Gerald Victor Horner; Thomas Arthur Craggs
Original assignee: Eta Process Plant Limited
Priority date: 1992-06-13
Filing date: 1993-06-14
Publication date: 1993-12-23
Also published as: GB2267849B; GB2267849A; GB9212607D0

Abstract

A liquid distribution mechanism, for example for the delivery of sewage slurry into a settlement tank, comprises a distribution device mounted for rotational movement about a vertical axis, comprising a central well (10), from which four outlet troughs (12) extend radially. Mounted in the well (10), and disposed in a uniform radial array around a central area are a plurality of curved baffles. Extending through the central part of the well (10) is a fixed pressure conduit (22), provided with twin outlets (24a, 24b), said outlets being so disposed as to direct flow of fluid under pressure against the baffles (20), to cause the distribution device to rotate about said axis. Liquid then flows into the well, and flows along the troughs, through outlets thereof, to be distributed around the settlement tank.

Description

Title: Liquid Distribution Mechanism Description of Invention

This invention in concerned with improvements relating to liquid distribution mechanisms, particularly of the kind as are utilised to distribute liquid containing suspended solids (in the form of a slurry) over an irrigation bed.

In a number of applications is it desired to distribute liquid generally continuously and uniformly over an irrigation bed. For example in the aerobic treatment of sewage, a slurry containing suspended solids is delivered to a tower containing packing elements upon which bacteria grows, the tower being perhaps 3 to 40 metres in diameter. Conventionally to so distribute the slurry a liquid distribution mechanism is used comprising a plurality of radially extending arms provided with nozzles, the slurry being fed to the arms under high pressure, so that the liquid on exiting of the arms causes the mechanism to rotate under reaction pressure.

The rate at which the mechanism rotates is thus dependent upon the size of the nozzles, and difficulty is encountered when the nozzles become blocked, since it is common practice to provide the mechanism with a relatively airtight seal.

According to this invention there is provided a liquid distribution mechanism comprising a housing, a distribution device comprising at least one liquid outlet mounted on the housing for rotary movement, and a conduit through which liquid under pressure flows towards the distribution device, rotary movement of the device being produced by liquid flowing through the mechanism prior to flow from the outlet of the distribution device.

In this manner the outlet need not be small to produce a high reaction force to rotate the device, and may be sufficiently large to permit flow of solid materials carried by the liquid. Indeed, the outlet may be provided in a conduit which is open, e.g. in the form of an open trough.

Preferably rotation is produced by impingement of liquid flow on members producing rotary movement of the distribution device, e.g. upon baffles. In this manner solids carried by the liquid need not impair the efficiency of operation, as would be the case were rotary forces produced by reaction forces, i.e. forces dependent upon the utilisation of nozzles of small size.

Preferably the distribution device comprises a plurality of baffles against which liquid impinges from the conduit. Thus, the conduit may comprise one or more outlets so arranged that liquid flowing therefrom impinges against the baffles, causing rotational forces to be exerted against the distribution device, prior to flow of liquid into the well. Preferably the number of baffles is a non-integral multiple of the number of outlets, e.g. if the number of outlets is two, the number of baffles is odd, so that one baffle is always positioned more closely to one outlet than the others.

Preferably a large number of baffles is provided to obtain a high transmission of force, e.g. greater than four baffles, preferably greater than eight baffles, and advantageously about sixteen.

Preferably the baffles are curved, e.g. involute, to increase the effectiveness of the liquid jet applied thereto.

Conveniently the mechanism comprises two pressure pumps, whereby both may be used initially to obtain sufficient flow to cause rotation of the distribution device up to a desired speed (e.g. between 1 and 2m/sec), but one only is utilised to maintain rotation at a steady speed. It has been found that a centrifugal pump may be utilised to maintain a desired constancy of rotation, e.g. to within 10%.

Preferably the distribution device comprises radially opposed arms, each being in the form of an open-topped outlet trough, extending from a central well, into which liquid flows from the conduit, flow into the outlet troughs being under gravity with some centrifugal component.

Preferably each outlet trough is provided with a plurality of outlet openings, preferably of V-shape in side walls defining the trough.

Preferably in each outlet trough the openings are arranged along a line inclined at an acute angle to the axis of the trough, preferably such that the apices of the openings lie uniformly spaced from a water line adopted by liquid in the trough during rotation at the desired speed.

Thus preferably the apices of the outlet openings lie on a hyperbola, such that liquid will flow substantially uniformly from each of the outlet openings, although if one becomes temporarily blocked, flow of liquid will cause such solids to rise towards the part of the opening of greater size.

Preferably the mechanism comprises four radially opposed arms, each extending from the central well, conveniently all in the same vertical plane.

According to this invention there is also provided a liquid distribution mechanism comprising a pressure flow line through which fluid to be distributed is fed under pressure, an outlet device through which fluid flows from the pressure flow line, the outlet device being provided with at least one outlet through which fluid flows from the mechanism, rotation of the distribution device being produced by flow of liquid from the pressure flow line towards the outlet device.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of a liquid distribution mechanism which is the preferred embodiment of this invention, having been selected for the purposes of illustrating the invention by way of example.

In the accompanying drawings:-

Figure 1 is a vertical sectional view showing part of the mechanism which is the preferred embodiment of the invention;

Figure 2 is an enlarged view of a central part of the mechanism;

Figure 3 is a horizontal sectional view of the mechanism; and

Figure 4 is an enlarged view illustrating part of an outlet trough of the preferred embodiment.

The mechanism which is the preferred embodiment of the invention is for distributing liquid in the form of sewage slurry into a settlement tank, for the aerobic digestion of the suspended solids by bacteria growing on packing elements contained in the tank, the tank being between 3 and 40 metres in diameter, and the mechanism distributing liquid uniformly over the top of the treatment bed.

The mechanism comprises a central housing 6, which is fixed in relation to the treatment tank over a central part thereof, the housing having mounted thereon, for rotary movement, an outlet device 8. The outlet device comprises a cylindrical chamber 8 providing a central well 10, from which four outlet troughs 12 extend radially, the outlet troughs being supported by cables 14 attached to an upper part of the housing, and fixed to collars 16 carried by the outlet troughs 12.

Mounted in the well 10, and disposed in a uniform radial array around a central area are a plurality, specifically 17, curved baffles 20.

Extending through the central part of the chamber is a fixed pressure conduit 22, said conduit being connected at its upper end to the fixed housing 6, and being provided with twin outlets 24a, 24b, said outlets being so disposed as to direct flow of fluid under pressure against the baffles 20. Thus, on flow of fluid under pressure through the baffles 22, a component of force on the outlet device^" is produced to cause rotational movement thereof relative to the housing 6.

The outlet troughs 12 are of open-topped construction, and are provided in side walls thereof with V-shaped openings 30 (see Figure 4). The apices of the openings lie on a high hyperbola, as is shown.

The mechanism which is the preferred embodiment of the invention comprises two supply pumps, a starter pump and a steady state pump (not shown) to deliver fluid under pressure from a supply through the conduit 22. Initially when the mechanism is at rest, a higher flow rate of fluid through the outlets 24a and 24b is required to produce rotation of the outlet device 8 to the required speed, and thereafter the steady state device, which may conveniently be a centrifugal pump, will be sufficient to retain the device rotating at a substantial constant speed. Alternatively a single, variable displacement pump may be used.

At steady state, the well 10 is substantially filled with fluid, the fluid flowing into the four outlet troughs 12 primarily under gravity, and partly due to the action of centrifugal forces. Liquid in the troughs will thus adopt a level, shown by the chain dotted line A in Figure 4, from which the apices of the outlets 30 are spaced by a generally uniform distance, so as to ensure in general terms a uniform flow from the outlets 30 into the treatment tank. Should one or more of the outlets 30 become blocked by solid material, the level of fluid in the trough will rise to carry the solid material to a higher point on the outlet 30, which is of larger size, to allow the solid material to flow, and at worst, liquid will flow over the top of the troughs. Should for any reason the outlets require cleaning, this can be done relatively easily by the use of a hose.

Whilst the mechanism which is the preferred embodiment of the invention has been described in relation to the distribution of liquid afforded by a sewage slurry, it is to be appreciated that the mechanism may be utilised in other liquid treatment plants, where similar or analogous problems arise, particularly in relation to the treatment of industrial effluent.

Additionally, whilst in the preferred embodiment the baffles are shown disposed in the central well 10 in an annular array around the pressure conduit 22, they may of course-be adopted at a different location within the well, provided that the flow of liquid under pressure from the outlet 24a and 24b can act on the baffles with sufficient force to produce rotation of the outlet device.

In the preferred embodiment two outlets nozzles 24a and 24b are shown, but this may of course be increased as desired, and the number of baffles may be increased or decreased. Preferably however the number of baffles is other than an integral multiple of the number of outlets 24, differing therefrom e.g. by one, to increase the likelihood of a baffle being disposed opposite to an outlet 24 on start-up of the mechanism.

In the use of the mechanism which is the preferred embodiment of the invention, it has been found that a desired rotational rate may be achieved relatively easily, said desired rate being such as to achieve a velocity of between 1 and 2 m/sec at the tips of the arms 12, and retained to within an accuracy of 10%, allowing a flow rate of 250 litres per second of sewage slurry to be obtained. Whilst in the preferred embodiment the outlet openings are of triangular form arranged to lie on a hyperbola, they may lie on a substantially horizontal line allowing a range of rotational speeds to be used.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A liquid distribution mechanism comprising a housing, a distribution device comprising at least one liquid outlet mounted on the housing for rotary movement, and a conduit through which liquid under pressure flows towards the distribution device, rotary movement of the device being produced by liquid flowing through the mechanism prior to flow from the outlet of the distribution device.

2. A mechanism according to Claim 1 wherein impingement of liquid on at least one member produces rotary movement of the distribution device.

3. A mechanism according to Claim 2 comprising a plurality of baffles, against which liquid is impinged as it flows from the conduit.

4. A mechanism according to Claim 3 wherein the conduit is provided with two outlets, from each of which liquid flows, to be directed against said baffles.

5. A mechanism according to one of Claims 3 and 4 wherein said baffles are curved.

6. A mechanism according to any one of the preceding claims comprising two pressure pumps to deliver liquid through said conduit, one of said pumps being a steady state pump.

7. A mechanism according to any one of Claims 1 to 5 comprising a variable displacement pump to feed liquid under pressure to said conduit.

8. A mechanism according to any one of the preceding claims wherein the distribution device comprises radially opposed arms in the form of open- topped troughs extending from a central well, into which liquid flows from the conduit.

9. A mechanism according to Claim 8 wherein each trough is provided with a plurality of outlet openings in side walls of the troughs.

10. A mechanism according to Claim 9 wherein apices of the openings lie uniformly spaced from a water line adopted by liquid in the trough during rotation of the distribution device at the desired speed.